OLYMPIA (AP) — Republican Rep. Dave Reichert of Auburn said Wednesday that he is retiring from Congress after seven terms.

Reichert, 67, a former sheriff famous for his decadeslong, successful hunt for the Green River serial killer convicted of killing 49 women, has represented a suburban district east of Seattle since 2005. After new district lines were approved in 2012, his district crossed the Cascade Mountain range and added areas in more conservative central Washington.

Reichert said in a written statement that his decision not to seek re-election was difficult, but added, "I believe it was the right one for my family and me. I have spent my entire career and devoted my life to service. I see this not just as a job, but as a calling — a calling I will not walk away from."

Reichert said he was especially proud of his work to expand the Alpine Lakes Wilderness Area, improve the foster care system, combat sex trafficking and secure equipment and resources for first responders.

House Speaker Paul Ryan referred to Reichert by his Capitol nickname of "Sheriff," and in a written statement said he was "an invaluable public servant and has inspired us all, myself especially."

Reichert served two terms as sheriff of King County before being elected to Congress. He was the first detective assigned to the Green River killings and was sheriff when Gary Ridgway was arrested.

Ridgway was convicted in 2003 of killing 49 women, but he said he likely committed more than 71 murders. He is serving a sentence of life without parole.

Democrats had targeted Reichert, with a host of would-be challengers lining up to seek the party's support in a district that Hillary Clinton won by 3 percentage points last year. Clinton received strong support in heavily populated King County, while President Donald Trump won support in the 8th Congressional District's portion of Chelan, Douglas, Kittitas and Pierce counties.

Rep. Steve Stivers of Ohio, chairman of the National Republican Congressional Committee, said he was confident that the seat would remain in GOP hands, especially with "a bitter and expensive primary fight already confronting Democrats" in the district.

Reichert easily won a seventh term last year, beating former sportscaster Tony Ventrella.

Even so, Democrats have targeted the district in 2018, citing voter concerns about health care and immigration and record disapproval ratings for Trump.

"Clearly, Congressman Reichert saw the writing on the wall, and realized that he was in for an uphill re-election campaign against a strong bench of Democratic challengers with a motivated base, while defending congressional Republicans' failed legislative agenda, particularly on health-care repeal," said Drew Godinich, a spokesman for the Democratic Congressional Campaign Committee.

Chris Vance, a Republican consultant and former U.S. Senate candidate who lives in the district, said an open seat isn't a slam dunk for Democrats but noted that the district is considered a swing district that slightly leans Republican.

Reichert, first elected in 2004, is the third Republican elected to the district since its creation after the 1980 census. However, it tipped for Clinton in the presidential election and favored Democratic U.S. Sen. Patty Murray over Vance, her challenger.

"It is by far the most vulnerable of the four Republican districts" in Washington state, Vance said. "And it's going to be Trump, Trump, Trump, Trump, Trump."